1. Field of the Invention
The present invention relates generally to gas turbine engines and, more particularly, to a structural frame component in a turbine engine using a plurality of yokes for attaching the outer ends of radial struts to the outer casing of the frame component.
2. Description of the Prior Art
Gas turbine engines typically include a core engine having a compressor for compressing air entering the core engine, a combustor where fuel is mixed with the compressed air and then burned to create a high energy gas stream, and a first or high pressure turbine which extracts energy from the gas stream to drive the compressor. In aircraft turbofan engines, a second turbine or low pressure turbine located downstream from the core engine extracts more energy from the gas stream for driving a forward fan. The forward fan provides the main propulsive thrust generated by the engine.
The static parts of a gas turbine engine, namely, frames, casings and mounts, are components that do not rotate but instead provide the overall backbone of the engine. These static components must maintain alignment between the rotors and stators of the engine. In many instances, this requirement dictates a need for stiffness, rather than strength, in the construction of the frames.
A structural frame component in a turbine engine is a static part that supports bearings which, in turn, support the rotatable rotors of the engine. The typical elements of a structural frame component, such as one located between the high and low pressure turbines of the engine, are an outer casing, an inner hub, and a plurality of circumferentially-spaced generally radial struts extending between the shells. The outer casing and inner hub are also commonly referred to as outer and inner rings or shells.
To protect frame struts from gases at high temperatures, for example 1900.degree. F., flowing in the flowpath from the high pressure turbine to the low pressure turbine, an air-cooled, aerodynamically-shaped fairing or nozzle encases each of the frame struts. The nozzles are assembled about the frame struts by placing them over the outer ends of the struts. This must be carried out before the struts are attached to the outer casing. Thus, a mechanical connection of some type must be provided between the outer ends of the struts and the outer shell which can be readily assembled after the nozzles have first been installed over the struts.
However, in order to minimize engine performance losses, the nozzles installed over the struts and the struts themselves must be as thin as possible. Unfortunately, there is not sufficient material at the strut ends to enable radial bolting to the outer casing. Consequently, a need exists for a mechanical connection between the outer ends of the struts and the outer casing having a design which will achieve these requirements.